Magna Carta, every schoolchild used to learn, was the foundation of English law and liberty. Extracted from bad King John by his barons through threat of force, it includes this undertaking:

Larry May's project is ‘inspired … by the signing of Magna Carta’ (4), and from the above provision which he quotes (25) he derives a legacy of four rights: ‘not to be arbitrarily imprisoned…not to be arbitrarily dispossessed or deprived of citizenship rights…not to be outlawed or exiled arbitrarily’ (25–6) and to trial by jury. These, he argues, are rights to due process of law rather than substantive rights to specific goods. As such they are preconditions for, and partly constitutive of, a rule of law, and much of May's book is taken up with arguing for the availability to all of such procedural rights.

It is the right not to be arbitrarily imprisoned, protected by the procedure of habeas corpus, to which May devotes most attention. Habeas corpus ensures that a prisoner is brought out of detention into public view and has the charges against him read out. May considers arguments for habeas corpus from its preventing prisoners from being ‘disappeared’ or from suffering torture (whose effects would be publicly apparent) and from its deterring tyrants from imprisoning their opponents without good grounds. While he finds some merit in these arguments, he believes that the principal justification of habeas corpus lies in what he calls ‘the principle of visibleness’, which acts as ‘a counter to the secrecy that masks the arbitrary exercise of power’ (100). It is ‘the normative idea that rulers must make their decisions transparent’, and as such it is ‘a protection of security’ (101). Thus procedural rights like habeas corpus, May claims, have an instrumental value in supporting rights to liberty and security, but also intrinsic value in constituting a rule of law which is fair and non-arbitrary.

May produces defences of the other rights he sees as part of Magna Carta's legacy, arguing for the right to be subject to international law, for non-refoulement – ‘the right not to be arbitrarily sent out of a country where one resided to another country where one was likely to be harmed’ (26) – and for the right to trial by jury. His motivation here, however, as with his defence of habeas corpus, is not just to exhibit what a rule of law would look like in the abstract. As well as the signing of Magna Carta, the other event by which his project is ‘inspired’ – in this instance a rather curious description – is ‘the establishment of US prisons at Guantanamo and Bagram’ (4) nearly 800 years later. In these prisons the rights granted in Magna Carta, and largely available in the USA, the UK and similar countries, have been comprehensively denied to inmates. What this fact demonstrates, May believes, is the existence of a gap in international law. For, while international law recognises many substantive rights, like those to liberty and security, it fails to provide the procedural rights through which they can be put into effect. His discussion of the four Magna Carta rights is, then, intended to indicate how this deficiency might be made good so that the rule of law actually prevailed at the international level.

Why is it additions to international law, rather than additions to the ordinary domestic law of states, that are required? May's answer is that there are people who do not in fact receive the protection afforded by procedural rights through domestic law, even where this is theoretically available, as well as those for whom this is not even theoretically available. May is concerned not only with the inmates of Guantanamo and Bagram but with immigrants in detention facilities and refugees in camps – people who are exposed to abuses for which they have no effective remedy. In order for them to receive the protection of the law that others enjoy, May argues, international law needs strengthening. For, although international treaties like the Universal Declaration of Human Rights or the International Covenant for Civil and Political Rights seek to offer rights against arbitrary imprisonment and so forth, ‘the current international institutional regime has been largely ineffective at the level of procedural rights’ (224). There are just are no effective procedures, May believes, through which those who have their rights violated can secure redress. So, in addition to advocating international recognition of such procedural rights, May proposes the creation of a world court of equity ‘to hear appeals from individual detainees who have not had their claims challenging the legitimacy of their detention heard or properly adjudicated in their home States or in regional courts’ (207).

Along the way, May discusses the nature of procedural rights and argues for their place as ‘a minimal moral core’ (78) of the law, upon which both H. L. A. Hart and Lon Fuller could agree despite their theoretical differences. May therefore believes that habeas corpus should be recognised in international law as jus cogens – a norm from which no derogation is permissible. Among the ills to which he applies his remedy of international procedural rights are collective punishment, rendition and forced statelessness. He ends the book with a consideration of the appeal to security considerations as a supposed reason for not granting such rights, though here it is slightly surprising that he does not discuss the UK debate over Control Orders upon terrorist suspects not brought to trial, in which reference to Magna Carta was frequently made by opponents of this form of detention.

It will be evident that May's book covers a great deal of ground over some very varied terrain. It makes use of diverse methods, not only deploying moral reasoning in arguing its case but relying on jurisprudential considerations to advocate the extension and institutional realisation of existing principles of international law. In many ways this eclectic methodology is an attractive feature of the book. It militates against the all too common parading of a theoretical position from which solutions to practical problems, such as those that May sets out, are mechanically derived. His problem cases are inextricably bound up with questions about the law since they involve not only harms but wrongs, and wrongs of a sort we expect the law to rectify. Yet why do we expect a legal remedy to be available in them? It seems to be, as May persistently indicates, because the victims are not just treated badly but treated arbitrarily, and the rule of law is a defence against arbitrary treatment to which we do not believe that people should be subjected. But what exactly is wrong with arbitrariness?

At the time of Magna Carta's signing, historians tell us, ‘what men feared and resented in serfdom was not its subordination, but its arbitrariness’.Footnote ¹ And we should note that it was to freemen only, not to serfs, that the protections of Magna Carta were originally offered, and offered precisely to spare them the arbitrary treatment that could be meted out to serfs. But arbitrariness was feared because, in the theological thinking of the day, ‘the supremacy of Will was itself an evil, whether the will was one's own or another's’,Footnote ² by contrast with the rule of law by which free men were governed and general conformity to which constituted their freedom. We scarcely have such thoughts today, but I am not convinced that May's account is much more plausible. ‘Arbitrariness’, he tells us, ‘is a disvalue in the sense that it disrupts… predictability and ultimately disrupts the proper and respectful functioning of human agency’ (54). May's point seems more a Kantian than a consequentialist one, since to be subject to arbitrary treatment without being harmed is, he writes, ‘a loss concerning one's status as a human, and as a bearer of human rights’ (56). But to say, as he does later, that to be deprived of the protection of human rights is to be ‘effectively rendered not fully human’ (191) is not very helpful in explaining what it is about this status that makes arbitrary treatment intolerable.

Given that the notion of arbitrariness seems so central to May's argument it is disappointing that he does not give a more satisfying account of it. The unpredictability to which he adverts is the result of treatment which is arbitrary in the sense of being capricious. Yet, far from being capricious, one's jailer may be agonisingly predictable, his arbitrariness consisting, instead, in his having no good reason for one's imprisonment. It is surely this that Magna Carta rights are meant to counter; for the rule of law should aim to ensure that one is not simply subject to the will of another, with no good reason for one's treatment. And, for there to be a good reason for it, one's treatment cannot serve just his interests, but interests the claims of which one could oneself, in principle, appreciate. On an account such as this, then, arbitrariness would deny someone a reason for his treatment; and this sort of idea seems to me to provide a better foundation for the procedural rights for which May argues than that which he himself offers.

Yet do such rights need a theoretical underpinning of this kind anyway, with its almost irresistible temptation towards some questionable metaphysics of the human person? After all, ‘the barons of Magna Carta had little thought for generalities’,Footnote ³ though they no doubt shared the medieval mindset mentioned earlier. What concerned them were their own interests and those of their vassals, and they had the power to secure their interests through entering into this compact with the king. Curiously, May brings no comparable considerations to bear in recommending changes to international law. He writes as if we were disinterested observers of events, making moral judgments about them and expressing such sentiments as that ‘it must not be allowed that a State like the US could use the threat to national security as a mere pretext to detain individuals for lengthy periods of time… and to deprive them of habeas corpus appeal’ (227). Well, could we stop it? We are not, of course, just observers. We are participants in events, and it is as citizens of states whose security may be threatened, and which have different amounts of power, that we must weigh concerns for freedom against those for safety. This is a very different sort of process from May's, which aims, in the abstract, at a ‘compromise … where neither rights nor security should be unduly sacrificed for the other’ (228).

May's book is to be welcomed as opening up a neglected area for intellectual investigation in its advocacy of international procedural rights, and it should provoke some lively rejoinders. Its jurisprudential deliberations seem to me entirely appropriate since it is new laws that are being advocated. But it is, it appears to me, insufficiently reflective about how a distinctively philosophical consideration of this issue should proceed. No doubt we would like some extra-legal conceptualisation of what the new laws ought to accomplish. Yet in clarifying our thinking here May's book is, in my judgment, only a starting point.